JPH10259062A - Binder for dielectric material molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject binder that is excellent in press-adhesion with heat and gives green sheets that resist to the collapse on adhesion by selecting as a binder for making slurry for green sheets by mixing together with ceramic particles and an organic solvent, a copolymer of a specific molecular weight and containing a prescribed alkyl methacrylate, alkyl acrylate and fatty acid. SOLUTION: The binder is prepared from a 1-6C alkyl methacrylate, a 1-6C alkyl acrylate and a fatty acid, preferably from 55-90 wt.% of methyl methacrylate, 55-90 wt.% of butyl acrylate and the rest amount of acrylic acid and is a copolymer that has a number-average molecular weight Mn of 15,000-220, 000, a weight-average molecular weight Mw of 75,000-800,000 where Mw /Mn =2.6-6.7. The resultant green sheet is excellent in tensile strength and is suitable for production of condensers of high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer capacitor or the like.
The present invention relates to a binder for molding a dielectric material used when a ceramic sheet is formed by firing.

[0002]

2. Description of the Related Art A multilayer ceramic capacitor is manufactured by stacking and firing ceramic green sheets having electrodes printed on the surface. The internal electrodes formed so as to be alternately exposed at the respective edges of the capacitor are covered with a conductive material at the exposed ends, and the internal electrodes of all layers are connected. This forms a parallel connection group of capacitors. The green sheet is obtained by adding a binder made of an organic solvent and an organic polymer to the ceramic particles, further adding a plasticizer if necessary, and mixing the resulting slurry to a support such as a polyester film or stainless steel. Can be

In the case of a conventional doctor blade system, the thickness of the green sheet is adjusted by the gap between the blades and the speed of coating the support. Conventionally, as a binder for a green sheet, as described in Patent No. 2500808, etc., polyvinyl butyral, polyvinyl acetate, polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, methyl hydroxyethyl cellulose, polystyrene, polyvinyl pyrrolidone, polyamide, polyethylene oxide, polypropylene Oxides, polyacrylamides, polyacrylates, polymethacrylates, copolymers of acrylates and methacrylates, and the like have been used.

The viscosity of a slurry produced by mixing such a polymer binder is 40 to 3000 cps (Brookfield viscometer: NO. 1 spindle / NO.
2 spindle, 100 rpm / 50 rpm, 25 ° C.).

[0005]

The slurry has the highest content of ceramic and the lowest content of binder so that the viscosity falls within the above viscosity range. It is preferred in terms of.

[0006] When the binder is formed as a green sheet, it is a thin green sheet.
Lamination of multiple sheets, good pressure adhesion under heating, no green sheet crushing, high tensile strength of green sheet, good peelability of green sheet from support after drying Is required.

[0007] The conventional binder as it is cannot satisfy these requirements sufficiently, and in order to obtain a high-strength green sheet, the molecular weight must be increased. This causes problems such as poor performance. Further, in order to obtain an appropriate viscosity, the molecular weight must be reduced, but a very brittle green sheet results.

The present invention has been made in view of the above problems, and has as its object to provide a binder which has good adhesiveness of a green sheet, does not crush the green sheet during pressure bonding, and has high tensile strength. Aim.

[0009]

SUMMARY OF THE INVENTION The present invention provides a binder for molding a dielectric material, in which a ceramic particle is mixed with an organic solvent to form a slurry for forming a green sheet, wherein the monomer has 1 carbon atom. -6, an alkyl acrylate having 1 to 6 carbon atoms, and a fatty acid, and having a number average molecular weight M _N of 15,000 to 22,000.
0, a weight-average molecular weight M _W is 75000 to 800000, and a weight-average molecular weight M _W to the number average molecular weight M _N
The ratio M _W / M _N of characterized in that it is a copolymer of from 2.0 to 6.7 (claim 1).

In the present invention, the number average molecular weight is 1500
0 or a weight average molecular weight of 75,000
If it is less than 10, the tensile strength of the green sheet decreases, and the green sheet is easily broken. On the other hand, if the number average molecular weight exceeds 220000 or the weight average molecular weight is 80
If it exceeds 0000, the tensile strength increases, but the adhesion of the green sheet deteriorates.

Further, the ratio M _W / M _N of the weight-average molecular weight M _W to the number average molecular weight M _N is less than 2.0, the tensile strength becomes weak, also, the ratio M _W / M _N is 6. If the number 7 is below, the tensile strength and the pressure breaking strength can be secured.

Alkyl methacrylates and alkyl acrylates having about 1 to 6 carbon atoms are suitable for obtaining the aforementioned number average molecular weight and weight average molecular weight.
Particularly preferably, the binder comprises 55 to 90% by weight of methyl methacrylate and 10 to 4 parts of butyl acrylate.
More preferably, it is composed of 5% by weight and the balance of acrylic acid (claim 2). As the organic acid, maleic acid, itaconic acid or the like can be used in addition to acrylic acid.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A paint containing the components shown in Table 1 was placed in a ball mill container and mixed with zirconia balls for 12 hours to produce a ceramic-containing composition for producing a green sheet. In this case, the ratio of the monomer composition of the organic polymer was as shown in Table 2. (Below)

[0014]

[Table 1]

[0015]

[Table 2]

From this ceramic composition, a thickness of 30 μm
Green sheet, dried at 90 ° C. for 3 minutes,
The substrate was cut out into a substrate having a size of 50 mm × 50 mm, and heated and pressed at 25 ° C. and 40 ° C. while changing the pressure to 25 kg / cm ² and 50 kg / cm ² to obtain a laminate.

In Table 2, samples 1 to 3, 5 and 6 are comparative examples, and samples 4 and 7 are examples according to the present invention. In Table 2, the mark 良好 indicates that a laminated body with good adhesiveness and complete integration was obtained, the mark △ indicates that the adhesiveness was almost good and each sheet was almost completely adhered, and the mark × indicates adhesion. Indicates that the laminate is not formed due to a defect.

In addition, the sample No. One, two
In the composition (1), very good adhesion cannot be obtained with alkyl methacrylate alone (butyl methacrylate, methyl methacrylate).

The sample No. Comparative Examples 3 and 5 and Sample Nos. As can be seen from the comparison between Nos. 4 and 7, it is understood that better adhesion can be obtained by adding acrylic acid, which is a fatty acid, to these copolymers than forming copolymers using only butyl acrylate and methyl methacrylate.

Further, it can be seen that a copolymer comprising 55 to 90% by weight of methyl methacrylate, 10 to 45% by weight of butyl acrylate and the balance of acrylic acid has good adhesiveness.

Next, the polymer composition was changed to the sample No. 4, that is, a composition of 14% by weight of butyl acrylate, 1% by weight of acrylic acid, and 85% by weight of methyl methacrylate. Component paints in Table 1 were made using the organic polymers varied as shown in 8-14. Table 3 shows the heat-press adhesiveness of the green sheet.

The sample No. 8 to 14 green sheets were cut into substrates of 10 mm × 10 mm, and the tensile strength and pressure rupture strength of the green sheets were measured. In addition, the pressure breaking strength was examined by checking whether or not the green sheet was broken at the time of heating and pressing for forming a laminate. The results are also shown in Table 3.

[0023]

[Table 3]

As can be seen from Table 3, the number average molecular weight M _N
Is smaller, the tensile strength tends to decrease.
If more than 15000 number average molecular weight M _N shown in 8~14, 9.8kgf / cm ² or more tensile strength is being obtained. On the other hand, the sample No. As shown in 14, when the number average molecular weight M _N becomes 240,000, the adhesiveness in lamination deteriorates. Therefore, the number average molecular weight M _N is preferably set to 220000 or less.

The sample No. As can be seen from the comparison of 8,9, the weight average molecular weight M _W is in 75000M _W or more, is secured pressure fracture strength and the green sheet is not broken, the weight average molecular weight M _W is less than 75,000, pressure disruption Strength is reduced. On the other hand, the sample No. As can be seen from 13, 14, the weight average molecular weight M _W is more than 800,000, although the tensile strength is increased, the adhesion of the green sheet may deteriorate.

The sample No. As shown in 9, when the ratio of the weight average molecular weight M _W to the number average molecular weight M _N M _W / M _N is less than 2.0, the tensile strength becomes weak, also, samples NO. As shown in FIG. 11, it was confirmed that the tensile strength could be ensured even when the ratio M _W / M _N was 6.7 at the maximum.

[0027]

According to the binder of the present invention, when laminating a plurality of green sheets and laminating them under heat and pressure, the adhesiveness is good, and the green sheets are not crushed at the time of pressure bonding. Since the strength is high, high quality capacitors can be produced with high yield.

Claims (2)

[Claims] 1. A binder for forming a dielectric material, wherein a slurry for forming a green sheet is prepared by mixing ceramic particles with an organic solvent, wherein the monomer comprises alkyl methacrylate having 1 to 6 carbon atoms;
And alkyl acrylates having 1 to 6 carbon atoms, composed of a fatty acid, the number average molecular weight M _N is 15000 to 220000, weight-average molecular weight M _W is from 75,000 to 800,000, and number average molecular weight M _N of the weight-average molecular weight M _W against Ratio _MW /
The dielectric material forming binder for M _N is equal to or is a copolymer of from 2.0 to 6.7. 2. The dielectric material molding according to claim 1, wherein the copolymer of the binder comprises 55 to 90% by weight of methyl methacrylate, 10 to 45% by weight of butyl acrylate and the balance of acrylic acid. For binders.